JP2000225823A - Loading amount sensitive type hydraulic buffer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a damping force value corresponding to a loading state in also both elongation and contraction stroke when a hydraulic buffer is elongated and contracted by ruggedness of a road surface and to automatically change damping force by only loading amount, regardless of pressure fluctuation of a lower chamber. SOLUTION: A piston nut 4 and a sleeve 15 are fitted by providing a small diameter part and a large diameter part in each of upper and lower sides. In a small diameter fitting part, a seal 11 is interposed. Outflow from the inside 4B of an oil reservoir chamber formed between a small diameter part and a large diameter part in compression stroke at the time of heavy loading to an upper chamber A side is interrupted, and switching to low damping force at the time of light loading due to push-down of the sleeve 15 at the time of heavy loading is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber capable of automatically changing a damping characteristic in accordance with a loaded weight of a vehicle.

[0002]

2. Description of the Related Art In a hydraulic shock absorber used for a vehicle having a large load variation such as a light van or a truck including a two-wheeled vehicle and a four-wheeled vehicle, the damping force depends on the load state of the load. Is required to change characteristics. For example, a hydraulic shock absorber disclosed in Japanese Patent Publication No. 58-29416 realizes this characteristic.

In order to facilitate comparison with the present invention, FIG.
Is proposed to solve such a problem, where the left side from the center line shows a state where high damping force is generated during heavy loading, and the right side generates low damping force during light loading. Indicates the status.

[0004] The piston nut 4 and the sleeve 5 are fitted with a small-diameter portion and a large-diameter portion provided vertically, and an oil reservoir (dashpot) 4B is provided between the small-diameter portion and the large-diameter portion.
Is made gentle by a buffering effect when hydraulic oil enters and leaves the oil reservoir, so that a sudden change in the damping force can be prevented. As a result, FIG.
Problems such as a disturbance in the damping force waveform due to a sudden change in the damping force as shown in FIG. 3A are prevented, and the damping force changes smoothly as shown in FIG.

When the vehicle is lightly loaded, the suspension spring pushes up the vehicle body and the piston moves upward. The upper end of the position detecting spring 7 rising from the bottom of the cylinder 2 is connected to the outer surface of the piston nut 4. The sleeve 5 is detached from the lower end of the sleeve 5 fitted to the sleeve. For this reason, the sleeve 5 is moved downward by the pressing force of the reaction force spring 6, and is composed of the through hole 1A and the hollow hole 1B (hereinafter abbreviated as a hollow passage) of the piston rod and the through hole 4A of the piston nut. In addition, a bypass passage that bypasses the pressure side valve PVc and short-circuits the upper chamber A and the lower chamber B is opened.

When the bypass passage is opened, the hydraulic oil is supplied to the expansion valves PV arranged on both sides of the piston 3.
e and flows through the bypass passage bypassing the pressure side valve PVc, so that a low damping force is generated due to the passage resistance at that time. Since the oil reservoir chamber 4B has the same pressure as the lower chamber, the sleeve 5 is kept depressed at all times, and a low damping force at the time of light loading is stably generated in any of the expansion and contraction strokes.

On the other hand, when the vehicle is in a heavily loaded state, the upper end of the position detecting spring 7 rising from the bottom of the cylinder 2 comes into contact with the lower end of the sleeve 5 fitted on the outer surface of the piston nut 4, and 5 moves upward by the pushing force of the position detecting spring 7, so that the bypass passage is closed by the sleeve 5.

As a result, in the extension stroke, the upper chamber A
Hydraulic oil of the expansion valve PV disposed opposite the lower annular window 3C communicating with the upper chamber A via the expansion port 3A.
e is pushed open to flow out into the lower chamber B, and the passage resistance at this time generates a high extension side damping force. On the other hand, in the contraction stroke, the hydraulic oil in the lower chamber B pushes open the pressure side valve PVc disposed opposite the upper annular window 3D communicating with the lower chamber B via the pressure side port 3B, and flows out to the upper chamber A. However, a high pressure side damping force is generated due to the passage resistance at this time.

[0009]

As described above, in the extension stroke in the heavy load state, the pressures of the upper chamber A, the oil reservoir 4B, and the lower chamber B are set to P1, P2, and P3, respectively. Comparing the chamber pressures, P1≫P2> P3. Fitting gap δ between piston nut 4 and sleeve 5
2, the hydraulic oil in the upper chamber A having a high pressure flows into the oil reservoir 4B through the through hole 4A of the piston nut.
The sleeve 5 stably generates a high damping force while being pushed upward.

However, when switching to the contraction stroke, the pressure in the lower chamber B increases due to the pressure side valve (not shown) at the lower end of the cylinder. As a result, the hydraulic oil in the oil storage chamber 4B flows out through the fitting gap δ2 to the upper chamber A having a low pressure, and the magnitude of the pressure suddenly changes to P3≫P2> P1.
The downward thrust obtained by multiplying the pressure receiving area of B by the differential pressure (P3−P2) overcomes the repulsive force of the spring (the pushing force of the position detecting spring 7−the pushing force of the reaction force spring 6), and during the above-described extension stroke. Conversely, the spool moves down,
Since it switches to a low damping force at the time of light loading, the shock absorption in the heavy loading state becomes insufficient, and the riding comfort of the vehicle deteriorates.

The present invention has been made in view of the above-described circumstances, and an object of the present invention is to cope with a situation where a hydraulic shock absorber expands and contracts due to unevenness of a road surface and the like, and a load state can be accommodated in both expansion and contraction strokes. It is an object of the present invention to provide a hydraulic shock absorber in which the adjusted damping force value is maintained, and the damping force automatically changes only depending on the load amount without being influenced by the pressure fluctuation of the lower chamber B.

[0012]

According to the present invention, a piston fastened to a lower end portion of a piston rod by a piston nut is movably inserted into a cylinder in which a position detecting spring is raised from a bottom portion. Is divided into an upper chamber and a lower chamber, and a piston is formed with an extension port and a compression port that communicate the two chambers. A pressure side valve is provided on the upper surface opening window so as to be openable and closable, and a bypass passage that bypasses the extension side and the pressure side valve and short-circuits the upper chamber and the lower chamber with a hollow passage formed in the piston rod. A through-hole formed in the piston nut, the base end of which is formed by a downward biasing force of a reaction force spring supported on the piston side and a repulsion force of the position detection spring. In which the hydraulic shock absorber "that vertically movably fitted a sleeve which communicates or blocks the bypass passage to the outer surface of the piston nut assumed.

A first means adopted by the present invention to solve the above problem is that the piston nut and the sleeve are fitted with a small-diameter portion and a large-diameter portion provided respectively at the top and bottom, and the small-diameter fitting portion is provided. A seal is interposed between the oil reservoir and the upper chamber to prevent the oil from flowing out from the oil reservoir formed between the small-diameter portion and the large-diameter portion during the compression stroke during heavy loading. Switching to a lower damping force. " The second means is that the piston nut and the sleeve are fitted with upper and lower small-diameter portions and large-diameter portions, respectively, and the fitting portion has an oil formed between the small-diameter portion and the large-diameter portion. That is, the storage chamber and the pressure introducing chamber that guides the pressure of the lower chamber are provided in the small-diameter fitting section, and the annular gap that buffers the vertical movement of the sleeve is provided in the small-diameter fitting section. "

[0014]

FIG. 1 shows a first embodiment of the present invention which solves the above-mentioned problems. The feature of the present embodiment is that the piston nut 4 and the sleeve 15 are fitted with a small diameter portion and a large diameter portion provided at the top and bottom, respectively, and the small diameter portion of the sleeve 15 fitted on the outer periphery of the piston nut 4 (or the piston nut). The outer periphery of the small-diameter portion of FIG.

As shown in FIG. 1, the seal 11 is interposed between the small-diameter fitting portion of the sleeve 15 and the piston nut 4 to reduce the pressure affecting the pressure (P2) of the oil reservoir chamber 4B by the large-diameter fitting. Only the pressure (P3) of the lower chamber B through the section was set. By doing so, the relationship between the pressure (P3) in the lower chamber B and the pressure (P2) in the oil reservoir 4B becomes P3> P2, and there is no outflow from the oil reservoir 4B to the upper chamber A. In this case, when the hydraulic shock absorber is compressed, the sleeve 15 is pushed downward to open a bypass passage that short-circuits the upper chamber A and the lower chamber B, and the damping force is switched to a low damping force at light loading. It is possible to prevent the occurrence of a problem such as the occurrence of a problem.

FIG. 2 shows a second embodiment of the present invention. The feature of this embodiment is that the piston nut 4 and the sleeve 25 are fitted with a small diameter portion and a large diameter portion provided respectively on the upper and lower sides, and an oil reservoir formed between the small diameter portion and the large diameter portion is fitted to the fitting portion. Room 4B,
A pressure introducing chamber 25B communicating with the lower chamber B through a through hole 25A is formed in the inner peripheral side fitting portion of the small diameter portion of the sleeve 25, while the fitting portion of the sleeve 25 and the piston nut 4 moves the sleeve 25 up and down. Is formed.

As a result, the pressure affecting the oil reservoir 4B is the pressure (P3) of the lower chamber B via the annular gap δ3.
Only. The relationship between the pressure (P3) in the lower chamber B and the pressure (P2) in the oil reservoir 4B is P3> P2, and there is no outflow from the oil reservoir 4B, so the hydraulic shock absorber is compressed when the vehicle is in a heavy load state. At this time, it is possible to prevent a problem that the sleeve 25 is pushed down to open the bypass passage and the damping force is switched to the low damping force at the time of light loading.

In any of the above embodiments, the damping force is automatically switched in accordance with the load capacity, and even if the hydraulic shock absorber expands and contracts due to the impact of road surface irregularities, etc. Since the sleeve moves up and down slowly due to the buffer effect of the formed oil reservoir, the damping force is not frequently switched in response to the unevenness of the road surface, and a stable damping force can be generated during traveling.

[0019]

As described in detail above, in the first embodiment of the present invention, the seal is interposed on the inner peripheral side of the small diameter portion of the sleeve (or the outer peripheral side of the small diameter portion of the piston nut), and the second embodiment is also provided. In the above, by forming a pressure introduction chamber communicating with the lower chamber B in the small diameter portion inner peripheral side fitting portion of the sleeve, when the vehicle is in a heavy load state and the hydraulic shock absorber is compressed, the sleeve 15 is moved downward. , The bypass passage is opened and the damping force is switched to a low damping force at the time of light loading, thereby preventing occurrence of a problem. In addition, the sleeve 15
Gently moves, so that the damping force is not frequently switched in response to the unevenness of the road surface, and a stable damping force can be generated during traveling.

[Brief description of the drawings]

FIG. 1 is a sectional view near a piston of a hydraulic shock absorber according to a first embodiment of the present invention.

FIG. 2 is a sectional view near a piston of a hydraulic shock absorber according to a second embodiment of the present invention.

FIG. 3A is an example of a damping force waveform in which a failure has occurred. (B) It is an example of a normal damping force waveform.

FIG. 4 is a sectional view showing the vicinity of a piston of a hydraulic shock absorber according to the related art.

[Explanation of symbols]

 A upper chamber B lower chamber PVe extension side valve PVc pressure side valve δ3 annular gap 1 piston rod 1A, 1B hollow passage of piston rod 2 cylinder 3 piston 3A extension side port 3B pressure side port 3C (piston) bottom opening window 3D (of piston) ) Top opening window 4 Piston nut 4A Piston nut through hole 4B Oil reservoir chamber 5, 15, 25 Sleeve 6 Reaction force spring 7 Position detection spring 11 Seal 25B Pressure introduction chamber 1A, 1B, 4A Bypass passage

Claims (2)

[Claims] 1. A piston fastened to a lower end of a piston rod by a piston nut is movably inserted into a cylinder in which a position detecting spring is raised from a bottom, and the piston divides the cylinder into an upper chamber and a lower chamber. The piston has an extension port and a compression port communicating the two chambers, and an extension valve is provided on the lower opening window at the lower end of the extension port.
A pressure-side valve is provided in the upper opening window at the upper end of the pressure-side port so as to be openable and closable, and a bypass passage that bypasses the extension side and the pressure-side valve and short-circuits the upper chamber and the lower chamber is formed in the piston rod. The bypass is constituted by a hollow passage provided in the piston nut and a through hole formed in the piston nut, and a base end portion of the bypass is formed by a biasing force of a reaction force spring supported on the piston side and a repulsion force of the position detection spring. In a hydraulic shock absorber in which a sleeve for communicating or blocking a passage is vertically movably fitted to an outer surface of a piston nut, the piston nut and the sleeve are fitted with a small-diameter portion and a large-diameter portion provided at the top and bottom, respectively. A seal is interposed in the joint to prevent the oil from flowing out of the oil reservoir chamber formed between the small-diameter portion and the large-diameter portion to the upper chamber side during the compression stroke during heavy loading. A hydraulic shock absorber characterized in that it is prevented from being lowered and switched to a low damping force when lightly loaded. 2. A piston fastened to a lower end of a piston rod by a piston nut is movably inserted into a cylinder in which a position detecting spring stands up from a bottom, and the piston divides the inside of the cylinder into an upper chamber and a lower chamber. The piston has an extension port and a compression port communicating the two chambers, and an extension valve is provided on the lower opening window at the lower end of the extension port.
A pressure-side valve is provided in the upper opening window at the upper end of the pressure-side port so as to be openable and closable, and a bypass passage that bypasses the extension side and the pressure-side valve and short-circuits the upper chamber and the lower chamber is formed in the piston rod. The bypass is constituted by a hollow passage provided in the piston nut and a through hole formed in the piston nut, and a base end portion of the bypass is formed by a biasing force of a reaction force spring supported on the piston side and a repulsion force of the position detection spring. In a hydraulic shock absorber in which a sleeve for communicating or blocking a passage is vertically movably fitted to an outer surface of a piston nut, the piston nut and the sleeve are fitted with a small-diameter portion and a large-diameter portion provided above and below, respectively. The part has an oil reservoir formed between the small-diameter part and the large-diameter part, and a pressure-introducing chamber that guides the pressure of the lower chamber to the small-diameter fitting part. Buffer A damping force adjusting device for a hydraulic shock absorber, wherein an annular gap is provided.